Is she spayed? My first female had an hysterical pregnancy at that age and her coat got very thin/dry–it was at this time of year, too.
What are you feeding her--I usually go for a lower fat food (10-12% or so) and supplement generously with fresh Omega 3 rather than buying a kibble that contains it: it can go rancid quickly in kibble & cause diarrhea. I also split large bags of food into batches and keep it in the freezer. I've had a number of fosters arrive with very thin, brittle coats and that fill out beautifully with a quality Omega 3 supplement–the good stuff isn't cheap, but everyone remarks on my pack's shiny coats. Plus it's an anti-inflammatory, helps keep them young & healthy. As sighthounds, B's have less oily skin that's prone to dryness in winter climates
Also, foods with a lot of soy protein or phyto-estrogens can also cause coat thinning. So can environmental toxins: Febreeze, chemical spray cleaners like Lysol, scented candles & rug cleaners. I use a lot of vinegar, baking soda & lemon juice for cleaning.
Hope this helps!